Navigational control devices, such as joysticks for use with computer software, are known in the art. Conventional joysticks may include a housing with a user-positioned actuator handle pivoted about a fixed point to actuate electromechanical switches that generate X- and Y-axis data. In some joysticks, springs may be employed to return the actuator handle to a centered position. Such conventional joysticks typically require some type of opening in the housing through which the actuator handle extends. The opening, as well as openings in the switch itself, can allow dirt, water and other contaminants to enter the housing and become trapped within the switch. Certain environments contain a large volume of contaminants that can pass through the openings, causing electrical shorting or damage to the components. Further, electromechanical switches are subject to wear, mechanical failure, and slow reaction time due to their very nature as mechanical devices having moving parts.
Various alternatives to mechanical switches are known in the art, such as optical encoders, switch arrays, piezo-electric transducers, inductive coupling devices, and magnetic devices. However, the incorporation of such components in a joystick has not proven cost effective for consumer-oriented data input applications. Furthermore, they may unduly restrict actuator motion, thereby degrading user “feel.”
Field effect touch sensors have proven particular advantageous for many applications. Such field effect touch sensors are disclosed in U.S. Pat. No. 5,594,222 to Caldwell; U.S. Pat. No. 6,310,611 to Caldwell; and U.S. Pat. No. 6,320,282 to Caldwell, the disclosures of which are incorporated herein by reference. However, known touch sensors use one electrode pattern per sense point. Further, the field effect sensors disclosed in U.S. Pat. No. 6,320,282 also require one integrated control circuit per electrode pattern and, therefore, one integrated control circuit per sense point. As such, these designs may not be cost effective or practical for use with some devices requiring numerous sense points, such as navigational control devices or slide control devices.
There is a need for an apparatus that reduces the number of electrode patterns and integrated control circuits in field effect sensor applications, thereby reducing component cost and manufacturing cost, and improving reliability.